<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <div class="father">
    <div class="content"></div>
    <div class="sidebar"></div>
    <!-- <div class="clearfix"></div> -->
  </div>
  <div class="main"></div>
</body>
<style>
  .father{
    background-color: aqua;
    /* overflow: hidden; */
    /* float: left; */
    display: table;
  }
  /* .father::after {
    content: "";
    clear: both;
    display: table;
    height: 0;
  } */
  .content{
    height: 200px;
    width: 200px;
    background-color: blueviolet;
    float: left;
  }
  .sidebar{
    height: 200px;
    width: 200px;
    background-color: rgb(69, 65, 73);
    float: left;
  }
  /* .clearfix{
    clear: both;
  } */
  /* .main{
    height: 200px;
    width: 200px;
    background-color: black;
    clear:both
  } */
</style>
</html>